Halogenation of hydrocarbons is typically carried out either in the vapor phase or in the liquid phase. The vapor phase halogenation of hydrocarbons is a rapid reaction. However, it is observed that vapor phase reactions are highly exothermic and therefore need extreme care and control.
In contrast, liquid phase halogenation of hydrocarbons is safe but the rate of halogenation of hydrocarbons is usually quite low, which further necessitates the use of catalysts for accelerating the rate of reaction. The catalysts generally used for liquid phase halogenation of hydrocarbons include metallic chlorides and iodine. However, such catalysts inevitably cause severe environmental concerns such as discharged waste liquids, gases and the like.
To counter these environmental concerns, efforts have been made to use ultra violet radiation as a catalyst.
For instance, U.S. Pat. No. 4,102,760 discloses a method of chlorinating vinylidene fluoride polymer resin in the presence of an initiator compound, triethanolamine and ultraviolet radiation. U.S. Pat. No. 4,102,760 utilizes a quartz mercury vapor lamp having a minimum intensity of 450 watts which emits about 28% of its energy in the ultraviolet region as a source of ultraviolet light. Further, a water-jacketed quartz immersion well is used to separate the reaction medium from the quartz mercury vapor lamp.
U.S. Pat. No. 3,362,896 discloses a process for the chlorination of vinyl chloride polymers in liquid suspension through irradiation with visible or short wavelength light. The light source used in accordance with the U.S. Pat. No. 3,362,896 is a vapor/gas-based, high pressure mercury lamp.
GB1202229 discloses a process the preparation of chlorinated polyvinyl chloride wherein 100 W mercury lamp is used as a light source.
WO2013069542 discloses a process for producing a chlorinated vinyl chloride resin. The process includes chlorination of a vinyl chloride resin by irradiating with ultraviolet light. The ultraviolet light source used in accordance with WO2013069542 includes ultraviolet LED, an organic EL, an inorganic EL and an ultraviolet laser.
The filament-based or vapor/gas-based lamp used in the prior art as a source of UV light emits defused or multi-directional UV light that exhibits a high rate of intensity decay with distance. Accordingly, these lamps are incapable of inducing effective reactions which further lead to consumption of high amount of electrical power. Additionally, these lamps are bulky and have a short life period (8000-15000 hours).
Further, the use of such light sources may cause short and long term health hazards by way of UV radiations scattered in the immediate environment. Furthermore, reaction vessels made of quartz make the halogenation process and its apparatus expensive.
Thus, there is a need for a novel and economic process for halogenation of hydrocarbons. Further, there is also a need for an apparatus which will utilize low-intensity solid state lights for halogenation of hydrocarbons.